The value of a program project lies in the integration of the work of diverse investigators pursuing a unifying scientific goal. An instrumentation core becomes central to a program project by providing the shared technology, nurturing that technology, and supplying efficient means of communication. The aims of the Instrumentation Core support the over-arching goal of integrating investigators and methods and the critical but, more mundane, goal of obtaining the highest quality scientific data. Since the initiation of this program project, our emphasis has shifted away from the construction of electronic circuits and the development of biological measurement instrumentation to the development and maintenance of computer systems/networks and the integration of laboratory and ambulatory equipment with these systems/networks. We have increasingly recognized that it is more cost-effective to contract for special purpose equipment design and equipment modification. Similarly, we have evolved away from performing the programming of large special purpose signal detection and analysis packages to the use of commercially programmed packages. Our role has evolved into the testing of these packages and the development of special purpose routines that mesh with these packages to provide efficient data reduction and analyses geared specifically to the needs of the projects. This core supports the projects forming the program project in the areas of development, acquisition, and maintenance of software and instrumentation. The core is designed to consult and collaborate with other cores and the projects, as well as providing direct high-level technical service. Day-to-day activities ensure that the project hardware and software are current and operating appropriately. Typically such routine activities combine with technical consultation and 'hands-on' service whenever problems arise. The core, because of its role in developing and maintaining project software, is closely allied with the statistics core. This is particularly evident in areas such as data transfer, storage, and reduction. These activities will increase greatly given that data handling requirements inherent in the aims the current program project proposal. The volume of data generated by both brain imaging and ambulatory procedures generate massive data files that must be checked, transformed, and reduced without compromising our high standards for data integrity. We further view education as one aspect of the core. Our project laboratories retain a good competence level in computing and instrumentation; the core seeks to foster this independence by increasing the level of technical expertise within the staffs of the project laboratories. The core is located in Western Psychiatric Institute and Clinic, where an electronics laboratory serves as an office and workspace. The Core also has an office/work site in Engineering Hall adjacent to other program project offices and laboratories. Coordination of core activities is accomplished by a weekly meeting (currently Mondays from 3:45 to 5 pm). The prioritized activities assigned for the prior week are reviewed (See sample weekly activity sheet used to discuss tasks in Table 1), new activities are discussed as they are brought up by project personnel attending the meeting as well as core personnel, and a prioritized list of activities for the upcoming week is developed. Core staff is organized around their specialized skills rather than on a project basis. Mr. Eddy specializes in software support and acts as network administrator/systems manager for the computers in the project. He has additional special skills in the development of hardware- software interfaces. This function continues to be critical. Mr. Haff has special skills in computer languages permitting us to shift between web-based applications and desktop based applications. He has become proficient in the programming of hand-held computers for use with ecological momentary assessment. He is now also expert in writing small programs that facilitate the use of package programs aiding efficiency and 'tuning' them to our particular needs. Finally, Mr. Haff has the mathematical and programming skills to effectively support our imaging work (skill with UNIX, Matlab and SPM). Dr. Jennings serves as both supervisor and translator between scientific needs and technical solutions.